The Internet protocol (IP) multimedia subsystem (IMS) is an architectural framework for delivering IP-based multimedia services. A wireless transmit/receive unit (WTRU) may connect to an IMS through various access networks, including but not limited to networks based on technology such as universal mobile telecommunications system (UMTS) terrestrial radio access network (UTRAN), long term evolution (LTE), worldwide interoperability for microwave access (WiMax), or wireless local area network (WLAN) technology. The WTRU may access the IMS through a packet-switched (PS) domain. Through the use of IMS centralized services (ICS), the WTRU may additionally access IMS services via a circuit-switched (CS) domain.
In a third generation partnership project (3GPP) system that supports IMS, an inter-unit transfer (IUT) (i.e., media mobility) is performed by a WTRU that supports an IMS-session initiation protocol (SIP). An IUT allows a communication session to be transferred from one WTRU to another. There is no standardized solution for non-IMS terminals, (e.g., packet switched streaming (PSS) services capable terminals, real time streaming protocol (RTSP)/real time control protocol (RTCP) terminals, and/or hyper text transfer protocol (HTTP) streaming terminals). Not all systems support IMS, and not all terminals are capable of supporting SIP, and therefore IUT operation for non-IMS terminals and in non-IMS systems may not be supported in a variety of instances.